U.S. Pat. No. 5,483,934 discloses a method of operating a four-stroke internal combustion engine with externally supplied ignition and direct injection and an arrangement for carrying out the method. In FIG. 2 of this publication, the entire operating range of the engine is subdivided into different ranges according to rpm and load and, depending upon the actual operating range, fuel is either injected during the induction stroke or during the compression stroke. For the injection during the induction stroke, a substantially homogeneous fuel distribution (homogeneous operation) results because of the time available until the ignition as well as because of the turbulence of the injected fuel. On the other hand, in the case of the injection in the compression stroke, a stratified charge (stratified charge operation) occurs. In this known arrangement, an electronic control apparatus provides for the switchover between homogeneous and stratified charge operations based upon the individual operating variables and predetermined criteria and further determines the injection values.
U.S. Pat. No. 5,558,178 relates to a method and arrangement for controlling a vehicle. Interfaces are provided between different component systems of which one is an engine control system. Data is exchanged via these interfaces on the basis of torques to control the vehicle.
In German patent application 196 18 385, a control arrangement is disclosed for influencing the air supply to an internal combustion engine wherein a desired value is pregiven for the torque or the power of the engine at least on the basis of the driver command and this desired value is converted into a desired adjusting value for an actuator device influencing the air supply. In the conversion, corrective factors are considered for the influence of additional operating mean flows which cannot be influenced by the actuator device and/or which represent the pressure and temperature conditions in the intake pipe. From the torque desired value or power desired value, a desired value for the charge of the cylinders is formed while considering the engine rpm. From this charge, a desired value for the air mass flow for the air mass flowing into the cylinders is derived. Furthermore, an air mass controller or charge controller is provided which forms a corrective value from the desired air mass flow or the desired charging value in accordance with the corresponding actual value. The corrective value is superposed on the desired value and, in this way, forms the desired air mass flow at the intake pipe input. This desired air mass flow at the intake pipe input is corrected with additional air mass flows such as leakage air and/or the air mass flow via a tank-venting valve to form the desired air mass flow at the actuator device. This desired air mass flow at the actuator device is converted into a desired volume flow while considering the pressure condition forward of and rearward of the throttle flap and the pressure forward of the throttle flap and/or the temperature of the air forward of the throttle flap. A desired angle for the actuator device is derived from the desired volume flow in accordance with a pregiven characteristic line.
A control arrangement for a direct-injecting internal combustion engine is described in U.S. patent application ser. No. 08/812,633, filed Mar. 7, 1997. This control arrangement includes sensors for operating characteristic variables, a signal processing unit as well as actuating devices for at least fuel, fuel pressure, air mass and ignition and furthermore includes the possibility of an operation of the fuel injection in the stratified charge or homogeneous operations depending upon the operating range of the engine. Here, a desired engine torque is converted into a value for the fuel flow. A value for the air mass flow is determined from this value for the fuel flow. The injection time values are adjusted in dependence upon the fuel flow depending upon stratified charge operation or homogeneous operation and the throttle flap position is adjusted depending upon the air mass flow. For the conversion of the engine torque into the fuel mass flow value, at least the rpm as well as an efficiency signal of the engine, which is dependent upon the operation present (stratified charge operation, homogeneous operation) is utilized. The efficiency is then obtained from the torque/rpm characteristic fields in dependence upon the particular mode of operation (stratified charge/homogeneous).
Stratified charge/homogeneous operation in the context of direct injected gasoline engines is discussed also in the SAE Paper 970624 of G. Karl et al entitled "Analysis of a Direct Injected Gasoline Engine".
Engines with gasoline direct injection are basically lean engines (that is, engines operated with a lean mixture). The advantage with respect to consumption results, inter alia, from a greatest possible unthrottled operation, that is, the lack of the losses at the throttle flap. Three operating states result for optimizing the consumption while, at the same time, controlling the combustion, and therefore the emissions, as well as making adequate power available:
1. extremely lean operation with charge stratification via late injection of fuel; PA1 2. moderately lean operation with homogeneous air/fuel mixture; and, PA1 3. stoichiometric operation with throttling.
The change between these operating states (which should occur very rapidly because of emission reasons) is however problematic with reference to the relationship between accelerator pedal and torque because, at the switchover point, a change of the engine torque results which is not wanted by the driver (dependency of torque on the air/fuel ratio).